The present invention relates to gripping devices.
More particularly this invention concerns hydraulic or pneumatic gripping devices provided with a differential pressure cylinder.
It is known in the prior art of pressuremedium operated gripping devices to provide a cylinder with a piston which is movable longitudinally within the cylinder. Such gripping devices are used for example for clamping, pressing, cutting or stamping, etc., a workpiece.
Such a device is described for example in German Offelegungsschrift No. 22 22 686 and is designed accordingly for gripping automobile body parts and includes a pneumatically or hydraulically longitudinally movable piston connected with correspondingly movable gripping, holding and connecting members. These members are actuated very fast and immediately with full predetermined force. During movement of these movable parts there very likely to occur undesired accidents which can cause different injuries to the operators or simply damages to the movable automobile body parts. Therefore, it is quite advantageous and sometimes simply necessary to control and regulate movement of the piston in order to substantially or entirely eliminate any likelihood of the mentioned accidents and injuries.
It has been recognized that the known gripping arrangements cannot promptly recognize and avert an unexpected situation in which accidents, injuries or any other unexpected disturbance are very likely to occur.